Shutter ink jet

ABSTRACT

An ink jet printer uses an actuator and an oscillating pressured ink supply. A shutter is located between the ink supply and an ink ejection port, normally blocking the ink ejection port. An actuator is provided for moving the shutter mechanism on demand away from the ink ejection port so as to allow for the ejection of ink on demand from the ink ejection port. The actuator includes a thermal actuator in a coiled form constructed primarily from polytetrafluorethylene. The coil is uncoiled upon heating. The actuator includes a serpentine heater element encased in a material having a high coefficient of thermal expansion. The serpentine heater takes a concertina form upon heating and a thick return trace returns the actuator to its original position upon cooling.

BACKGROUND OF THE INVENTION

[0001] Many different types of printing have been invented, a largenumber of which are presently in use. The known forms of print have avariety of methods for marking the print media with a relevant markingmedia. Commonly used forms of printing include offset printing, laserprinting and copying devices, dot matrix type impact printers, thermalpaper printers, film recorders, thermal wax printers, dye sublimationprinters and ink jet printers both of the drop on demand and continuousflow type. Each type of printer has its own advantages and problems whenconsidering cost, speed, quality, reliability, simplicity ofconstruction and operation etc.

[0002] In recent years, the field of ink jet printing, wherein eachindividual pixel of ink is derived from one or more ink nozzles hasbecome increasingly popular primarily due to its inexpensive andversatile nature.

[0003] Many different techniques on ink jet printing have been invented.For a survey of the field, reference is made to an article by J Moore,Non-Impact Printing: Introduction and Historical Perspective, OutputHard Copy Devices, Editors R Dubeck and S Sherr, pages 207-220 (1988).

[0004] Ink Jet printers themselves come in many different types. Theutilisation of a continuous stream ink in ink jet printing appears todate back to at least 1929 wherein U.S. Pat. No. 1,941,001 by Hanselldiscloses a simple form of continuous stream electrostatic ink jetprinting.

[0005] U.S. Pat. No. 3,596,275 by Sweet also discloses a process of acontinuous ink jet printing including the step wherein the ink jetstream is modulated by a high frequency electrostatic field so as tocause drop separation. This technique is still used by severalmanufacturers including Elmjet and Scitex (see also U.S. Pat. No.3,373,437 by Sweet et al)

[0006] Piezoelectric ink jet printers are also one form of commonly usedink jet printing device. Piezoelectric systems are disclosed by Kyseret. al. in U.S. Pat. No. 3,946,398 (1970) which discloses a diaphragmmode of operation, by Zolten in U.S. Pat. No. 3,683,212 (1970) whichdiscloses a squeeze mode of operation of a piezoelectric crystal, Stemmein U.S. Pat. No. 3,747,120 (1972) which discloses a bend mode ofpiezoelectric operation, Howkins in U.S. Pat. No. 4,459,601 whichdiscloses a piezoelectric push mode actuation of the ink jet stream andFischbeck in U.S. 4,584,590 which discloses a shear mode type ofpiezoelectric transducer element.

[0007] Recently, thermal ink jet printing has become an extremelypopular form of ink jet printing. The ink jet printing techniquesinclude those disclosed by Endo et al in GB 2007162 (1979) and Vaught etal in U.S. Pat. No. 4,490,728. Both the aforementioned referencesdisclose ink jet printing techniques rely upon the activation of anelectrothermal actuator which results in the creation of a bubble in aconstricted space, such as a nozzle, which thereby causes the ejectionof ink from an aperture connected to the confined space onto a relevantprint media. Printing devices using the electro-thermal actuator aremanufactured by manufacturers such as Canon and Hewlett Packard.

[0008] As can be seen from the foregoing, many different types ofprinting technologies are available. Ideally, a printing technologyshould have a number of desirable attributes. These include inexpensiveconstruction and operation, high speed operation, safe and continuouslong term operation etc. Each technology may have its own advantages anddisadvantages in the areas of cost, speed, quality, reliability, powerusage, simplicity of construction operation, durability and consumables.

SUMMARY OF THE INVENTION

[0009] It is an object of the present invention to provide analternative form of ink jet printing using an actuator and a shutteredoscillating pressured ink supply.

[0010] In accordance with the first aspect of the present invention,there is provided an ink jet nozzle comprising an ink ejection port forthe ejection of ink, an ink supply with an oscillating ink pressureinterconnected to the ink ejection port, a shutter mechanisminterconnected between the ink supply and the ink ejection port, whichblocks the ink ejection port, and an actuator mechanism for moving theshutter mechanism on demand away from the ink ejection port so as toallow for the ejection of ink on demand from the ink ejection port.

[0011] Further, the actuator comprises a thermal actuator which isactivated by the heating of one side of the actuator. Preferably theactuator has a coiled form and is uncoiled upon heating. The actuatorincludes a serpentine heater element encased in a material having a highcoefficient of thermal expansion. The serpentine heater concertinas uponheating. Advantageously, the actuator includes a thick return trace forthe serpentine heater element. The material in which the serpentineheater element is encased comprises polytetrafluoroethylene. Theactuator is formed within a nozzle chamber which is formed on a siliconwafer and ink is supplied to the ejection port through channels etchedthrough the silicon wafer.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Notwithstanding any other forms which may fall within the scopeof the present invention, preferred forms of the invention will now bedescribed, by way of example only, with reference to the accompanyingdrawings in which:

[0013]FIG. 1 is an exploded perspective view illustrating theconstruction of a single ink jet nozzle in accordance with the preferredembodiment;

[0014]FIG. 2 is a perspective view, partly in section, of a single inkjet nozzle constructed in accordance with the preferred embodiment;

[0015]FIG. 3 provides a legend of the materials indicated in FIGS. 4 to16;

[0016]FIG. 4 to FIG. 16 illustrate sectional views of the manufacturingsteps in one form of construction of an ink jet printhead nozzle; and

[0017]FIG. 17 shows a schematic, sectional end view of part of an inkjet nozzle array showing two nozzle arrangements of the array;

[0018]FIG. 18 shows the array with ink being ejected from one of thenozzle arrangements;

[0019]FIG. 19 shows a schematic side view of refilling of the nozzle ofthe first nozzle arrangement; and

[0020]FIG. 20 shows operation of the array preceding commencement of inkejection from the second of the illustrated nozzle arrangements.

DESCRIPTION OF PREFERRED AND OTHER EMBODIMENTS

[0021] In the preferred embodiment, an oscillating ink reservoirpressure is used to eject ink from ejection nozzles. Each nozzle has anassociated shutter which normally blocks the nozzle. The shutter ismoved away from the nozzle by an actuator whenever an ink drop is to befired.

[0022] Turning initially to FIG. 1, there is illustrated in explodedperspective a single ink jet nozzle 10 as constructed in accordance withthe principles of the present invention. The exploded perspectiveillustrates a single ink jet nozzle 10. Ideally, the nozzles are formedas an array on a silicon wafer 12. The silicon wafer 12 is processed soas to have two level metal CMOS circuitry which includes metal layersand glass layers 13 and which are planarised after construction. TheCMOS metal layer has a reduced aperture 14 for the access of ink fromthe back of silicon wafer 12 via an ink supply channel 15.

[0023] A bottom nitride layer 16 is constructed on top of the CMOS layer13 so as to cover, protect and passivate the CMOS layer 13 fromsubsequent etching processes. Subsequently, there is provided a copperheater layer 18 which is sandwiched between two polytetrafluoroethylene(PTFE) layers 19, 20. The copper layer 18 is connected to lower CMOSlayer 13 through vias 25, 26. The copper layer 18 and PTFE layers 19, 20are encapsulated within nitride borders e.g. 28 and nitride top layer 29which includes an ink ejection port 30 in addition to a number ofsacrificial etched access holes 32 which are of a smaller dimension thanthe ejection port 30 and are provided for allowing access of a etchantto lower sacrificial layers thereby allowing the use of the etchant inthe construction of layers, 18, 19, 20 and 28.

[0024] Turning now to FIG. 2, there is shown a cutaway perspective viewof a fully constructed ink jet nozzle 10. The ink jet nozzle uses anoscillating ink pressure to eject ink from ejection port 30. Each nozzlehas an associated shutter 31 which normally blocks it. The shutter 31 ismoved away from the ejection port 30 by an actuator 35 whenever an inkdrop is to be fired.

[0025] The ports 30 are in communication with ink chambers which containthe actuators 35. These chambers are connected to ink supply channels 15which are etched through the silicon wafer. The ink supply channels 15are substantially wider than the ports 30, to reduce the fluidicresistance to the ink pressure wave. The ink channels 15 are connectedto an ink reservoir. An ultrasonic transducer (for example, apiezoelectric transducer) is positioned in the reservoir. The transduceroscillates the ink pressure at approximately 100 KHz. The ink pressureoscillation is sufficient that ink drops would be ejected from thenozzle were it not blocked by the shutter 31.

[0026] The shutters are moved by a thermoelastic actuator 35. Theactuators are formed as a coiled serpentine copper heater 23 embedded inpolytetrafluoroethylene (PTFE) 19/20. PTFE has a very high coefficientof thermal expansion (approximately 770×10⁻⁶). The current return trace22 from the heater 23 is also embedded in the PTFE actuator 35, thecurrent return trace 22 is made wider than the heater trace 23 and isnot serpentine. Therefore, it does not heat the PTFE as much as theserpentine heater 23 does. The serpentine heater 23 is positioned alongthe inside edge of the PTFE coil, and the return trace is positioned onthe outside edge. When actuated, the inside edge becomes hotter than theoutside edge, and expands more. This results in the actuator 35uncoiling.

[0027] The heater layer 23 is etched in a serpentine manner both toincrease its resistance, and to reduce its effective tensile strengthalong the length of the actuator. This is so that the low thermalexpansion of the copper does not prevent the actuator from expandingaccording to the high thermal expansion characteristics of the PTFE.

[0028] By varying the power applied to the actuator 35, the shutter 31can be positioned between the fully on and fully off positions. This maybe used to vary the volume of the ejected drop. Drop volume control maybe used either to implement a degree of continuous tone operation, toregulate the drop volume, or both.

[0029] When data signals distributed on the printhead indicate that aparticular nozzle is turned on, the actuator 35 is energized, whichmoves the shutter 31 so that it is not blocking the ink chamber. Thepeak of the ink pressure variation causes the ink to be squirted out ofthe nozzle 30. As the ink pressure goes negative, ink is drawn back intothe nozzle, causing drop break-off. The shutter 31 is kept open untilthe nozzle is refilled on the next positive pressure cycle. It is thenshut to prevent the ink from being withdrawn from the nozzle on the nextnegative pressure cycle.

[0030] Each drop ejection takes two ink pressure cycles. Preferably halfof the nozzles 10 should eject drops in one phase, and the other half ofthe nozzles should eject drops in the other phase. This minimises thepressure variations which occur due to a large number of nozzles beingactuated.

[0031] Referring to FIGS. 17 to 20, the operation of the printhead isdescribed in greater detail. The printhead comprises an array of nozzlearrangements or nozzles 10, two of which are shown as 10.1 and 10.2 inFIG. 17. Each nozzle arrangement 10 has a chamber 58 in which itsassociated shutter 31 is arranged.

[0032] Each chamber 58 is in communication with an ink reservoir 60 viaan ink supply channel 36. An ultrasonic transducer in the form of apiezoelectric transducer 62 is arranged n the ink reservoir 60.

[0033] As described above, each ink drop ejection takes two ink pressurecycles. The two ink pressure cycles are referred to as a phase. Half ofthe nozzles 10 should eject ink drops 64 (FIG. 18) in one phase with theother half of the nozzles ejecting ink drops in the other phase.

[0034] Consequently, as shown in FIG. 17 of the drawings, the shutter31.2 of the nozzle 10.2 is in an open position while the shutter 31.1 ofthe nozzle 10.1 is in its closed position. It will be appreciated thatthe nozzle 10.2 represents all the open nozzles of the array of theprinthead while the nozzle 10.1 represents all the closed nozzles of thearray of the printhead.

[0035] In a first pressure cycle, the transducer 62 is displaced in thedirection of arrows 66 imparting positive pressure to the ink 57 in thereservoir 60 and, via the channels 36, the chambers 58 of the nozzles10. Due to the fact that the shutter 31.2 of the nozzle 10.2 is open,ink in the ink ejection port 30.2 bulges outwardly as shown by themeniscus 68. After a predetermined interval, the transducer 62 reversesdirection to move in the direction of arrows 70 as shown in FIG. 18 ofthe drawings. This causes necking, as shown at 72, resulting inseparation of the ink drop 64 due to a first negative going pressurecycle imparted to the ink 57.

[0036] In the second positive pressure cycle, as shown in FIG. 19 of thedrawings, with the transducer moving again in the direction of arrow 66,the positive pressure applied to the ink results in a refilling of thechamber 58.2 of the nozzle 10.2. It is to be noted that the shutter 31.2is still in an open position with the shutter 31.1 still being in aclosed position. In this cycle, no ink is ejected from either nozzle10.1 or 10.2.

[0037] Before the second negative pressure cycle, as shown in FIG. 20 ofthe drawings, the shutter 31.2 moves to its closed position. Then, asthe transducer 62 again moves in the direction of arrows 70 to impartnegative pressure to the ink 57, a slight concave meniscus 74 is formedat both ink ejection ports 30.1 and 30.2 However, due to the fact thatboth shutters 31.1 and 31.2 are closed, withdrawal of ink from thechambers 58.1 and 58.2 of the nozzles 10.1 and 10.2, respectively, isinhibited.

[0038] The amplitude of the ultrasonic transducer can be altered inresponse to the viscosity of the ink (which is typically affected bytemperature), and the number of drops which are to be ejected in thecurrent cycle. This amplitude adjustment can be used to maintainconsistent drop size in varying environmental conditions.

[0039] The drop firing rate can be around 50 KHz. The ink jet head issuitable for fabrication as a monolithic page wide printhead. FIG. 2shows a single nozzle of a 1600 dpi printhead in up shooterconfiguration.

[0040] Returning again to FIG. 1, one method of construction of the inkjet print nozzles 10 will now be described. Starting with the bottomwafer layer 12, the wafer is processed so as to add CMOS layers 13 withan aperture 14 being inserted. The nitride layer 16 is laid down on topof the CMOS layers so as to protect them from subsequent etchings.

[0041] A thin sacrificial glass layer is then laid down on top ofnitride layers 16 followed by a first PTFE layer 19, the copper layer 18and a second PTFE layer 20. Then a sacrificial glass layer is formed ontop of the PTFE layer and etched to a depth of a few microns to form thenitride border regions 28. Next the top layer 29 is laid down over thesacrificial layer using the mask for forming the various holes includingthe processing step of forming the rim 40 on nozzle 30. The sacrificialglass is then dissolved away and the channel 15 formed through the waferby means of utilisation of high density low pressure plasma etching suchas that available from Surface Technology Systems.

[0042] One form of detailed manufacturing process which can be used tofabricate monolithic ink jet printheads operating in accordance with theprinciples taught by the present embodiment can proceed using thefollowing steps:

[0043] 1. Using a double sided polished wafer 12, complete drivetransistors, data distribution, and timing circuits using a 0.5 micron,one poly, 2 metal CMOS process 13. The wafer is passivated with 0.1microns of silicon nitride 16. This step is shown in FIG. 4. Forclarity, these diagrams may not be to scale, and may not represent across section though any single plane of the nozzle. FIG. 3 is a key torepresentations of various materials in these manufacturing diagrams,and those of other cross referenced ink jet configurations.

[0044] 2. Etch nitride and oxide down to silicon using Mask 1. This maskdefines the nozzle inlet below the shutter. This step is shown in FIG.5.

[0045] 3. Deposit 3 microns of sacrificial material 50 (e.g. aluminum orphotosensitive polyimide)

[0046] 4. Planarize the sacrificial layer to a thickness of 1 micronover nitride. This step is shown in FIG. 6.

[0047] 5. Etch the sacrificial layer using Mask 2. This mask defines theactuator anchor point 51. This step is shown in FIG. 7.

[0048] 6. Deposit 1 micron of PTFE 52.

[0049] 7. Etch the PTFE, nitride, and oxide down to second level metalusing Mask 3. This mask defines the heater vias 25, 26. This step isshown in FIG. 8.

[0050] 8. Deposit the heater 53, which is a 1 micron layer of aconductor with a low Young's modulus, for example aluminum or gold.

[0051] 9. Pattern the conductor using Mask 4. This step is shown in FIG.9.

[0052] 10. Deposit 1 micron of PTFE 54.

[0053] 11. Etch the PIFE down to the sacrificial layer using Mask 5.This mask defines the actuator and shutter This step is shown in FIG.10.

[0054] 12. Wafer probe. All electrical connections are complete at thispoint, bond pads are accessible, and the chips are not yet separated.

[0055] 13. Deposit 3 microns of sacrificial material 55. Planarize usingCMP

[0056] 14. Etch the sacrificial material using Mask 6. This mask definesthe nozzle chamber wall 28. This step is shown in FIG. 11.

[0057] 15. Deposit 3 microns of PECVD glass 56.

[0058] 16. Etch to a depth of (approx.) 1 micron using Mask 7. This maskdefines the nozzle rim 40. This step is shown in FIG. 12.

[0059] 17. Etch down to the sacrificial layer using Mask 6. This maskdefines the roof of the nozzle chamber, the nozzle 30, and thesacrificial etch access holes 32. This step is shown in FIG. 13.

[0060] 18. Back-etch completely through the silicon wafer (with, forexample, an ASE Advanced Silicon Etcher from Surface Technology Systems)using Mask 7. This mask defines the ink inlets 15 which are etchedthrough the wafer. The wafer is also diced by this etch. This step isshown in FIG. 14.

[0061] 19. Etch the sacrificial material. The nozzle chambers arecleared, the actuators freed, and the chips are separated by this etch.This step is shown in FIG. 15.

[0062] 20. Mount the printheads in their packaging, which may be amolded plastic former incorporating ink channels which supply theappropriate color ink to the ink inlets at the back of the wafer. Thepackage also includes a piezoelectric actuator attached to the rear ofthe ink channels. The piezoelectric actuator provides the oscillatingink pressure required for the ink jet operation.

[0063] 21. Connect the printheads to their interconnect systems. For alow profile connection with minimum disruption of airflow, TAB may beused. Wire bonding may also be used if the printer is to be operatedwith sufficient clearance to the paper.

[0064] 22. Hydrophobize the front surface of the printheads.

[0065] 23. Fill the completed printheads with ink 57 and test them. Afilled nozzle is shown in FIG. 16.

[0066] It would be appreciated by a person skilled in the art thatnumerous variations and/or modifications may be made to the presentinvention as shown in the preferred embodiment without departing fromthe spirit or scope of the invention as broadly described. The presentembodiment is, therefore, to be considered in all respects to beillustrative and not restrictive.

[0067] The presently disclosed ink jet printing technology ispotentially suited to a wide range of printing systems including: colourand monochrome office printers, short run digital printers, high speeddigital printers, offset press supplemental printers, low cost scanningprinters, high speed pagewidth printers, notebook computers with inbuiltpagewidth printers, portable colour and monochrome printers, colour andmonochrome copiers, colour and monochrome facsimile machines, combinedprinter, facsimile and copying machines, label printers, large formatplotters, photograph copiers, printers for digital photographicminilabs, video printers, PhotoCD printers, portable printers for PDAs,wallpaper printers, indoor sign printers, billboard printers, fabricprinters, camera printers and fault tolerant commercial printer arrays.

[0068] Ink Jet Technologies

[0069] The embodiments of the invention use an ink jet printer typedevice. Of course many different devices could be used. Howeverpresently popular ink jet printing technologies are unlikely to besuitable.

[0070] The most significant problem with thermal ink jet is powerconsumption. This is approximately 100 times that required for highspeed, and stems from the energy-inefficient means of drop ejection.This involves the rapid boiling of water to produce a vapor bubble whichexpels the ink. Water has a very high heat capacity, and must besuperheated in thermal ink jet applications. This leads to an efficiencyof around 0.02%, from electricity input to drop momentum (and increasedsurface area) out.

[0071] The most significant problem with piezoelectric ink jet is sizeand cost. Piezoelectric crystals have a very small deflection atreasonable drive voltages, and therefore require a large area for eachnozzle. Also, each piezoelectric actuator must be connected to its drivecircuit on a separate substrate. This is not a significant problem atthe current limit of around 300 nozzles per printhead, but is a majorimpediment to the fabrication of pagewidth printheads with 19,200nozzles.

[0072] Ideally, the ink jet technologies used meet the stringentrequirements of in-camera digital color printing and other high quality,high speed, low cost printing applications. To meet the requirements ofdigital photography, new ink jet technologies have been created. Thetarget features include:

[0073] low power (less than 10 Watts)

[0074] high resolution capability (1,600 dpi or more)

[0075] photographic quality output

[0076] low manufacturing cost

[0077] small size (pagewidth times minimum cross section)

[0078] high speed (<2 seconds per page).

[0079] All of these features can be met or exceeded by the ink jetsystems described below with differing levels of difficulty. Forty-fivedifferent ink jet technologies have been developed by the Assignee togive a wide range of choices for high volume manufacture. Thesetechnologies form part of separate applications assigned to the presentAssignee as set out in the table under the heading Cross References toRelated Applications.

[0080] The ink jet designs shown here are suitable for a wide range ofdigital printing systems, from battery powered one-time use digitalcameras, through to desktop and network printers, and through tocommercial printing systems.

[0081] For ease of manufacture using standard process equipment, theprinthead is designed to be a monolithic 0.5 micron CMOS chip with MEMSpost processing. For color photographic applications, the printhead is100 mm long, with a width which depends upon the ink jet type. Thesmallest printhead designed is IJ38, which is 0.35 mm wide, giving achip area of 35 square mm. The printheads each contain 19,200 nozzlesplus data and control circuitry.

[0082] Ink is supplied to the back of the printhead by injection moldedplastic ink channels. The molding requires 50 micron features, which canbe created using a lithographically micromachined insert in a standardinjection molding tool. Ink flows through holes etched through the waferto the nozzle chambers fabricated on the front surface of the wafer. Theprinthead is connected to the camera circuitry by tape automatedbonding.

[0083] Tables of Drop-on-Demand Ink Jets

[0084] Eleven important characteristics of the fundamental operation ofindividual ink jet nozzles have been identified. These characteristicsare largely orthogonal, and so can be elucidated as an elevendimensional matrix. Most of the eleven axes of this matrix includeentries developed by the present assignee.

[0085] The following tables form the axes of an eleven dimensional tableof ink jet types.

[0086] Actuator mechanism (18 types)

[0087] Basic operation mode (7 types)

[0088] Auxiliary mechanism (8 types)

[0089] Actuator amplification or modification method (17 types)

[0090] Actuator motion (19 types)

[0091] Nozzle refill method (4 types)

[0092] Method of restricting back-flow through inlet (10 types)

[0093] Nozzle clearing method (9 types)

[0094] Nozzle plate construction (9 types)

[0095] Drop ejection direction (5 types)

[0096] Ink type (7 types)

[0097] The complete eleven dimensional table represented by these axescontains 36.9 billion possible configurations of ink jet nozzle. Whilenot all of the possible combinations result in a viable ink jettechnology, many million configurations are viable. It is clearlyimpractical to elucidate all of the possible configurations. Instead,certain ink jet types have been investigated in detail. These aredesignated IJ01 to IJ45 above which matches the docket numbers in thetable under the heading Cross References to Related Applications.

[0098] Other ink jet configurations can readily be derived from theseforty-five examples by substituting alternative configurations along oneor more of the 11 axes. Most of the IJ01 to IJ45 examples can be madeinto ink jet printheads with characteristics superior to any currentlyavailable ink jet technology.

[0099] Where there are prior art examples known to the inventor, one ormore of these examples are listed in the examples column of the tablesbelow. The IJ01 to IJ45 series are also listed in the examples column.In some cases, a print technology may be listed more than once in atable, where it shares characteristics with more than one entry.

[0100] Suitable applications for the ink jet technologies include: Homeprinters, Office network printers, Short run digital printers,Commercial print systems, Fabric printers, Pocket printers, Internet WWWprinters, Video printers, Medical imaging, Wide format printers,Notebook PC printers, Fax machines, Industrial printing systems,Photocopiers, Photographic minilabs etc.

[0101] The information associated with the aforementioned 11 dimensionalmatrix are set out in the following tables. Description AdvantagesDisadvantages Examples ACTUATOR MECHANISM (APPLIED ONLY TO SELECTED INKDROPS) Thermal An electrothermal Large force High power Canon Bubblejetbubble heater heats the ink to generated Ink carrier 1979 Endo et al GBabove boiling point, Simple limited to water patent 2,007,162transferring significant construction Low efficiency Xerox heater-in-heat to the aqueous No moving parts High pit 1990 Hawkins et ink. Abubble Fast operation temperatures al U.S. Pat. No. 4,899,181 nucleatesand quickly Small chip area required Hewlett-Packard forms, expellingthe required for actuator High mechanical TIJ 1982 Vaught et ink, stressal U.S. Pat. No. 4,490,728 The efficiency of the Unusual process is low,with materials required typically less than Large drive 0.05% of theelectrical transistors energy being Cavitation causes transformed intoactuator failure kinetic energy of the Kogation reduces drop. bubbleformation Large print heads are difficult to fabricate Piezo- Apiezoelectric crystal Low power Very large area Kyser et al U.S. Pat.No. electric such as lead consumption required for actuator 3,946,398lanthanum zirconate Many ink types Difficult to Zoltan U.S. Pat. No.(PZT) is electrically can be used integrate with 3,683,212 activated,and either Fast operation electronics 1973 Stemme expands, shears, orHigh efficiency High voltage U.S. Pat. No. 3,747,120 bends to applydrive transistors Epson Stylus pressure to the ink, required Tektronixejecting drops. Full pagewidth IJ04 print heads impractical due toactuator size Requires electrical poling in high field strengths duringmanufacture Electro- An electric field is Low power Low maximum SeikoEpson, strictive used to activate consumption strain (approx. Usui etall JP electrostriction in Many ink types 0.01%) 253401/96 relaxormaterials such can be used Large area IJ04 as lead lanthanum Low thermalrequired for actuator zirconate titanate expansion due to low strain(PLZT) or lead Electric field Response speed magnesium niobate strengthrequired is marginal (˜10 (PMN). (approx. 3.5 V/μm) μs) can be generatedHigh voltage without difficulty drive transistors Does not requirerequired electrical poling Full pagewidth print heads impractical due toactuator size Ferro- An electric field is Low power Difficult to IJ04electric used to induce a phase consumption integrate with transitionbetween the Many ink types electronics antiferroelectric (AFE) can beused Unusual and ferroelectric (FE) Fast operation materials such asphase. Perovskite (<1 μs) PLZSnT are materials such as tin Relativelyhigh required modified lead longitudinal strain Actuators requirelanthanum zirconate High efficiency a large area titanate (PLZSnT)Electric field exhibit large strains of strength of around 3 up to 1%associated V/μm can be readily with the AFE to FE provided phasetransition. Electro- Conductive plates are Low power Difficult to IJ02,IJ04 static plates separated by a consumption operate electrostaticcompressible or fluid Many ink types devices in an dielectric (usuallyair). can be used aqueous Upon application of a Fast operationenvironment voltage, the plates The electrostatic attract each other andactuator will displace ink, causing normally need to be drop ejection.The separated from the conductive plates may ink be in a comb or Verylarge area honeycomb structure, required to achieve or stacked toincrease high forces the surface area and High voltage therefore theforce. drive transistors may be required Full pagewidth print heads arenot competitive due to actuator size Electro- A strong electric fieldLow current High voltage 1989 Saito et al, static pull is applied to theink, consumption required U.S. Pat. No. 4,799,068 on ink whereupon Lowtemperature May be damaged 1989 Miura et al, electrostatic attraction bysparks due to air U.S. Pat. No. 4,810,954 accelerates the ink breakdownTone-jet towards the print Required field medium. strength increases asthe drop size decreases High voltage drive transistors requiredElectrostatic field attracts dust Permanent An electromagnet Low powerComplex IJ07, IJ10 magnet directly attracts a consumption fabricationelectro- permanent magnet, Many ink types Permanent magnetic displacingink and can be used magnetic material causing drop ejection. Fastoperation such as Neodymium Rare earth magnets High efficiency IronBoron (NdFeB) with a field strength Easy extension required. around 1Tesla can be from single nozzles High local used. Examples are: topagewidth print currents required Samarium Cobalt heads Copper (SaCo)and magnetic metalization should materials in the be used for longneodymium iron boron electromigration family (NdFeB, lifetime and lowNdDyFeBNb, resistivity NdDyFeB, etc) Pigmented inks are usuallyinfeasible Operating temperature limited to the Curie temperature(around 540 K) Soft A solenoid induced a Low power Complex IJ01, IJ05,IJ08, magnetic magnetic field in a soft consumption fabrication IJ10,IJ12, IJ14, core electro- magnetic core or yoke Many ink types Materialsnot IJ15, IJ17 magnetic fabricated from a can be used usually present ina ferrous material such Fast operation CMOS fab such as as electroplatediron High efficiency NiFe, CoNiFe, or alloys such as CoNiFe Easyextension CoFe are required [1], CoFe, or NiFe from single nozzles Highlocal alloys. Typically, the to pagewidth print currents required softmagnetic material heads Copper is in two parts, which metalizationshould are normally held be used for long apart by a spring.electromigration When the solenoid is lifetime and low actuated, the twoparts resistivity attract, displacing the Electroplating is ink.required High saturation flux density is required (2.0-2.1 T isachievable with CoNiFe [1]) Lorenz The Lorenz force Low power Force actsas a IJ06,IJ11,IJ13, force acting on a current consumption twistingmotion IJ16 carrying wire in a Many ink types Typically, only a magneticfield is can be used quarter of the utilized. Fast operation solenoidlength This allows the High efficiency provides force in a magneticfield to be Easy extension useful direction supplied externally to fromsingle nozzles High local the print head, for to pagewidth printcurrents required example with rare heads Copper earth permanentmetalization should magnets. be used for long Only the currentelectromigration carrying wire need be lifetime and low fabricated onthe print- resistivity head, simplifying Pigmented inks materials areusually requirements. infeasible Magneto- The actuator uses the Many inktypes Force acts as a Fischenbeck, striction giant magnetostrictive canbe used twisting motion U.S. Pat. No. 4,032,929 effect of materials Fastoperation Unusual IJ25 such as Terfenol-D (an Easy extension materialssuch as alloy of terbium, from single nozzles Terfenol-D are dysprosiumand iron to pagewidth print required developed at the Naval heads Highlocal Ordnance Laboratory, High force is currents required henceTer-Fe-NOL). available Copper For best efficiency, the metalizationshould actuator should be pre- be used for long stressed to approx. 8electromigration MPa. lifetime and low resistivity Pre-stressing may berequired Surface Ink under positive Low power Requires Silverbrook, EPtension pressure is held in a consumption supplementary force 0771 658A2 and reduction nozzle by surface Simple to effect drop related patenttension. The surface construction separation applications tension of theink is No unusual Requires special reduced below the materials requiredin ink surfactants bubble threshold, fabrication Speed may be causingthe ink to High efficiency limited by surfactant egress from the Easyextension properties nozzle. from single nozzles to pagewidth printheads Viscosity The ink viscosity is Simple Requires Silverbrook, EPreduction locally reduced to construction supplementary force 0771 658A2 and select which drops are No unusual to effect drop related patentto be ejected. A materials required in separation applications viscosityreduction can fabrication Requires special be achieved Easy extensionink viscosity electrothermally with from single nozzles properties mostinks, but special to pagewidth print High speed is inks can beengineered heads difficult to achieve for a 100:1 viscosity Requiresreduction, oscillating ink pressure A high temperature difference(typically 80 degrees) is required Acoustic An acoustic wave is CanOperate Complex drive 1993 Hadimioglu generated and without a nozzlecircuitry et al, EUP 550,192 focussed upon the plate Complex 1993 Elrodet al, drop ejection region. fabrication EUP 572,220 Low efficiency Poorcontrol of drop position Poor control of drop volume Thermo- An actuatorwhich Low power Efficient aqueous IJ03,IJ09,IJ17, elastic bend reliesupon differential consumption operation requires a IJ18,IJ19,IJ20,actuator thermal expansion Many ink types thermal insulator onIJ21,IJ22,IJ23, upon Joule heating is can be used the hot sideIJ24,IJ27,IJ28, used. Simple planar Corrosion IJ29,IJ30,IJ31,fabrication prevention can be IJ32,IJ33,IJ34, Small chip area difficultIJ35,IJ36,IJ37, required for each Pigmented inks IJ38,IJ39,IJ40,actuator may be infeasible, IJ41 Fast operation as pigment particlesHigh efficiency may jam the bend CMOS actuator compatible voltages andcurrents Standard MEMS processes can be used Easy extension from singlenozzles to pagewidth print heads High CTE A material with a very Highforce can Requires special IJ09,IJ17,IJ18, thermo- high coefficient ofbe generated material (e.g. PTFE) IJ20,IJ21,1122, elastic thermalexpansion Three methods of Requires a PTFE IJ23,IJ24,IJ27, actuator(CTE) such as PTFE deposition are deposition process, IJ28,IJ29,IJ30,polytetrafluoroethylen under development: which is not yetIJ31,IJ42,IJ43, e (PTFE) is used. As chemical vapor standard in ULSIIJ44 high CTE materials deposition (CVD), fabs are usually non- spincoating, and PTFE deposition conductive, a heater evaporation cannot befollowed fabricated from a PTFE is a with high conductive material iscandidate for low temperature (above incorporated. A 50 μm dielectricconstant 350° C.) processing long PTFE bend insulation in ULSI Pigmentedinks actuator with Very low power may be infeasible, polysilicon heaterand consumption as pigment particles 15 mW power input Many ink typesmay jam the bend can provide 180 μN can be used actuator force and 10 μmSimple planar deflection. Actuator fabrication motions include: Smallchip area Bend required for each Push actuator Buckle Fast operationRotate High efficiency CMOS compatible voltages and currents Easyextension from single nozzles to pagewidth print heads Conduct-ive Apolymer with a high High force can Requires special IJ24 polymercoefficient of thermal be generated materials thermo- expansion (such asVery low power development (High elastic PTFE) is doped with consumptionCTE conductive actuator conducting substances Many ink types polymer) toincrease its can be used Requires a PTFE conductivity to about 3 Simpleplanar deposition process, orders of magnitude fabrication which is notyet below that of copper. Small chip area standard in ULSI Theconducting required for each fabs polymer expands actuator PTFEdeposition when resistively Fast operation cannot be followed heated.High efficiency with high Examples of CMOS temperature (above conductingdopants compatible voltages 350° C.) processing include: and currentsEvaporation and Carbon nanotubes Easy extension CVD deposition Metalfibers from single nozzles techniques cannot Conductive polymers topagewidth print be used such as doped heads Pigmented inks polythiophenemay be infeasible, Carbon granules as pigment particles may jam the bendactuator Shape A shape memory alloy High force is Fatigue limits IJ26memory such as TiNi (also available (stresses maximum number alloy knownas Nitinol - of hundreds of MPa) of cycles Nickel Titanium alloy Largestrain is Low strain (1%) developed at the Naval available (more than isrequired to extend Ordnance Laboratory) 3%) fatigue resistance isthermally switched High corrosion Cycle rate between its weak resistancelimited by heat martensitic state and Simple removal its high stiffnessconstruction Requires unusual austenic state. The Easy extensionmaterials (TiNi) shape of the actuator from single nozzles The latentheat of in its martensitic state to pagewidth print transformation mustis deformed relative to heads he provided the austenic shape. Lowvoltage High current The shape change operation operation causesejection of a Requires pre- drop. stressing to distort the martensiticstate Linear Linear magnetic Linear Magnetic Requires unusual IJ12Magnetic actuators include the actuators can be semiconductor ActuatorLinear Induction constructed with materials such as Actuator (LIA),Linear high thrust, long soft magnetic alloys Permanent Magnet travel,and high (e.g. CoNiFe) Synchronous Actuator efficiency using Somevarieties (LPMSA), Linear planar also require Reluctance semiconductorpermanent magnetic Synchronous Actuator fabrication materials such as(LRSA), Linear techniques Neodymium iron Switched Reluctance Longactuator boron (NdFeB) Actuator (LSRA), and travel is available Requiresthe Linear Stepper Medium force is complex multi- Actuator (LSA).available phase drive circuitry Low voltage High current operationoperation BASIC OPERATION MODE Actuator This is the simplest Simpleoperation Drop repetition Thermal ink jet directly mode of operation:the No external rate is usually Piezoelectric ink pushes ink actuatordirectly fields required limited to around 10 jet supplies sufficientSatellite drops kHz. However, this IJ01,IJ02,IJ03, kinetic energy toexpel can be avoided if is not fundamental IJ04,IJ05,IJ06, the drop. Thedrop drop velocity is less to the method, but is IJ07,IJ09,IJ11, musthave a sufficient than 4 m/s related to the refill IJ12,IJ14,IJ16,velocity to overcome Can be efficient, method normally IJ20,IJ22,IJ23,the surface tension. depending upon the used IJ24,IJ25,IJ26, actuatorused All of the drop IJ27,IJ28,IJ29, kinetic energy must IJ30,IJ31,IJ32,be provided by the IJ33,IJ34,IJ35, actuator IJ36,IJ37,IJ38, Satellitedrops IJ39,IJ40,IJ41, usually form if drop IJ42,IJ43,IJ44 velocity isgreater than 4.5 m/s Proximity The drops to be Very simple printRequires close Silverbrook, EP printed are selected by head fabricationcan proximity between 0771 658 A2 and some manner (e.g. be used theprint head and related patent thermally induced The drop the print mediaor applications surface tension selection means transfer rollerreduction of does not need to May require two pressurized ink), providethe energy print heads printing Selected drops are required to separatealternate rows of the separated from the ink the drop from the image inthe nozzle by nozzle Monolithic color contact with the print print headsare medium or a transfer difficult roller. Electro- The drops to be Verysimple print Requires very Silverbrook, EP static pull printed areselected by head fabrication can high electrostatic 0771 658 A2 and onink some manner (e.g. be used field related patent thermally induced Thedrop Electrostatic field applications surface tension selection meansfor small nozzle Tone-Jet reduction of does not need to sizes is aboveair pressurized ink), provide the energy breakdown Selected drops arerequired to separate Electrostatic field separated from the ink the dropfrom the may attract dust in the nozzle by a nozzle strong electricfield. Magnetic The drops to be Very simple print Requires Silverbrook,EP pull on ink printed are selected by head fabrication can magnetic ink0771 658 A2 and some manner (e.g. be used Ink colors other relatedpatent thermally induced The drop than black are applications surfacetension selection means difficult reduction of does not need to Requiresvery pressurized ink), provide the energy high magnetic fields Selecteddrops are required to separate separated from the ink the drop from thein the nozzle by a nozzle strong magnetic field acting on the magneticink. Shutter The actuator moves a High speed (>50 Moving parts are IJ13,IJ17, IJ21 shutter to block ink kHz) operation can required flow to thenozzle. The be achieved due to Requires ink ink pressure is pulsedreduced refill time pressure modulator at a multiple of the Drop timingcan Friction and wear drop ejection be very accurate must be consideredfrequency. The actuator Stiction is energy can be very possible lowShuttered The actuator moves a Actuators with Moving parts are IJ08,IJIS, IJ18, grill shutter to block ink small travel can be required IJ19flow through a grill to used Requires ink the nozzle. The shutterActuators with pressure modulator movement need only small force can beFriction and wear be equal to the width used must be considered of thegrill holes. High speed (>50 Stiction is kHz) operation can possible beachieved Pulsed A pulsed magnetic Extremely low Requires an IJ10magnetic field attracts an ‘ink energy operation is external pulsed pullon ink pusher’ at the drop possible magnetic field pusher ejectionfrequency. An No heat Requires special actuator controls a dissipationmaterials for both catch, which prevents problems the actuator and thethe ink pusher from ink pusher moving when a drop is Complex not to beejected. construction AUXILIARY MECHANISM (APPLIED TO ALL NOZZLES) NoneThe actuator directly Simplicity of Drop ejection Most ink jets, firesthe ink drop, and construction energy must be including there is noexternal Simplicity of supplied by piezoelectric and field or otheroperation individual nozzle thermal bubble. mechanism required. Smallphysical actuator IJ01,IJ02,IJ03, size IJ04,IJ05,IJ07, IJ09,IJ11,IJ12,IJ14,IJ20,IJ22, IJ23,IJ24,IJ25, IJ26,IJ27,IJ28, IJ29,IJ30,IJ31,IJ32,IJ33,IJ34, IJ35,IJ36,IJ37, IJ38,IJ39,IJ40, IJ41,IJ42,IJ43, IJ44Oscillating The ink pressure Oscillating ink Requires externalSilverbrook, EP ink pressure oscillates, providing pressure can provideink pressure 0771 658 A2 and (including much of the drop a refill pulse,oscillator related patent acoustic ejection energy. The allowing higherInk pressure applications stimul- actuator selects which operating speedphase and amplitude IJ08,IJ13,IJ15, ation) drops are to be fired Theactuators must be carefully IJ17,IJ18,IJ19, by selectively may operatewith controlled IJ21 blocking or enabling much lower energy Acousticnozzles. The ink Acoustic lenses reflections in the ink pressureoscillation can be used to focus chamber must be may be achieved by thesound on the designed for vibrating the print nozzles head, orpreferably by an actuator in the ink supply. Media The print head is Lowpower Precision Silverbrook, EP proximity placed in close High accuracyassembly required 0771 658 A2 and proximity to the print Simple printhead Paper fibers may related patent medium. Selected construction causeproblems applications drops protrude from Cannot print on the print headfurther rough substrates than unselected drops, and contact the printmedium. The drop soaks into the medium fast enough to cause dropseparation. Transfer Drops are printed to a High accuracy BulkySilverbrook, EP roller transfer roller instead Wide range of Expensive0771 658 A2 and of straight to the print print substrates can Complexrelated patent medium. A transfer be used construction applicationsroller can also be used Ink can be dried Tektronix hot for proximitydrop on the transfer roller melt piezoelectric separation. ink jet Anyof the IJ series Electro- An electric field is Low power Field strengthSilverbrook, EP static used to accelerate Simple print head required for0771 658 A2 and selected drops towards construction separation of smallrelated patent the print medium, drops is near or applications above airTone-Jet breakdown Direct A magnetic field is Low power RequiresSilverbrook, EP magnetic used to accelerate Simple print head magneticink 0771 658 A2 and field selected drops of construction Requires strongrelated patent magnetic ink towards magnetic field applications theprint medium. Cross The print head is Does not require Requires externalIJ06,IJ16 magnetic placed in a constant magnetic materials magnet fieldmagnetic field. The to be integrated in Current densities Lorenz forcein a the print head may be high, current carrying wire manufacturingresulting in is used to move the process electromigration actuator.problems Pulsed A pulsed magnetic Very low power Complex print IJ10magnetic field is used to operation is possible head construction fieldcyclically attract a Small print head Magnetic paddle, which pushes sizematerials required in on the ink. A small print head actuator moves acatch, which selectively prevents the paddle from moving. ACTUATORAMPLIFICATION OR MODIFICATION METHOD None No actuator Operational Manyactuator Thermal Bubble mechanical simplicity mechanisms have Ink jetamplification is used. insufficient travel, IJ01,IJ02,IJ06, The actuatordirectly or insufficient force, IJ07,IJ16,IJ25, drives the drop toefficiently drive IJ26 ejection process. the drop ejection processDifferential An actuator material Provides greater High stresses arePiezoelectric expansion expands more on one travel in a reduced involvedIJ03,IJ09,IJ17, bend side than on the other. print head area Care mustbe IJ18,IJ19,IJ20, actuator The expansion maybe taken that theIJ21,IJ22,IJ23, thermal, piezoelectric, materials do not IJ24,IJ27,IJ29,magnetostrictive, or delaminate IJ30,IJ31,IJ32, other mechanism. TheResidual bend IJ33,IJ34,IJ35, bend actuator converts resulting from highIJ36,IJ37,IJ38, a high force low travel temperature or highIJ39,IJ42,IJ43, actuator mechanism to stress during IJ44 high travel,lower formation force mechanism. Transient A trilayer bend Very goodHigh stresses are IJ40,IJ41 bend actuator where the two temperaturestability involved actuator outside layers are High speed, as a Caremust be identical. This cancels new drop can be taken that the bend dueto ambient fired before heat materials do not temperature and dissipatesdelaminate residual stress. The Cancels residual actuator only respondsstress of formation to transient heating of one side or the other.Reverse The actuator loads a Better coupling Fabrication IJ05,IJ11spring spring. When the to the ink complexity actuator is turned off,High stress in the the spring releases. spring This can reverse theforce/distance curve of the actuator to make it compatible with theforce/time requirements of the drop ejection. Actuator A series of thinIncreased travel Increased Some stack actuators are stacked. Reduceddrive fabrication piezoelectric ink jets This can be voltage complexityIJ04 appropriate where Increased actuators require high possibility ofshort electric field strength, circuits due to such as electrostaticpinholes and piezoelectric actuators. Multiple Multiple smallerIncreases the Actuator forces IJ12,IJ13,IJ18, actuators actuators areused force available from may not add IJ20,IJ22,IJ28, simultaneously toan actuator linearly, reducing IJ42,IJ43 move the ink. Each Multipleefficiency actuator need provide actuators can be only a portion of thepositioned to control force required. ink flow accurately Linear Alinear spring is used Matches low Requires print IJ15 Spring totransform a motion travel actuator with head area for the with smalltravel and higher travel spring high force into a requirements longertravel, lower Non-contact force motion. method of motion transformationCoiled A bend actuator is Increases travel Generally IJ17,IJ21,IJ34,actuator coiled to provide Reduces chip restricted to planar IJ35greater travel in a area implementations reduced chip area. Planar dueto extreme implementations are fabrication difficulty relatively easy toin other orientations. fabricate. Flexure A bend actuator has a Simplemeans of Care must be IJ10,IJ19,IJ33 bend small region near theincreasing travel of taken not to exceed actuator fixture point, which abend actuator the elastic limit in flexes much more the flexure areareadily than the Stress remainder of the distribution is very actuator.The actuator uneven flexing is effectively Difficult to converted froman accurately model even coiling to an with finite element angular bend,resulting analysis in greater travel of the actuator tip. Catch Theactuator controls a Very low Complex IJ10 small catch. The catchactuator energy construction either enables or Very small Requiresexternal disables movement of actuator size force an ink pusher that isUnsuitable for controlled in a bulk pigmented inks manner. Gears Gearscan be used to Low force, low Moving parts are IJ13 increase travel atthe travel actuators can required expense of duration. be used Severalactuator Circular gears, rack Can be fabricated cycles are required andpinion, ratchets, using standard More complex and other gearing surfaceMEMS drive electronics methods can be used. processes Complexconstruction Friction, friction, and wear are possible Buckle plate Abuckle plate can be Very fast Must stay within S. Hirata et al, used tochange a slow movement elastic limits of the “An Ink-jet Head actuatorinto a fast achievable materials for long Using Diaphragm motion. It canalso device life Microactuator”, convert a high force, High stressesProc. IEEE MEMS, low travel actuator involved Feb. 1996, pp 418- into ahigh travel, Generally high 423. medium force motion. power requirementIJ18,IJ27 Tapered A tapered magnetic Linearizes the Complex IJ14magnetic pole can increase magnetic construction pole travel at theexpense force/distance curve of force. Lever A lever and fulcrum isMatches low High stress IJ32,IJ36,IJ37 used to transform a travelactuator with around the fulcrum motion with small higher travel traveland high force requirements into a motion with Fulcrum area has longertravel and no linear movement, lower force. The lever and can be usedfor can also reverse the a fluid seal direction of travel. Rotary Theactuator is High mechanical Complex IJ28 impeller connected to a rotaryadvantage construction impeller. A small The ratio of force Unsuitablefor angular deflection of to travel of the pigmented inks the actuatorresults in actuator can be a rotation of the matched to the impellervanes, which nozzle requirements push the ink against by varying thestationary vanes and number of impeller out of the nozzle. vanesAcoustic A refractive or No moving parts Large area 1993 Hadimioglu lensdiffractive (e.g. zone required et al, EUP 550,192 plate) acoustic lensis Only relevant for 1993 Elrod et al, used to concentrate acoustic inkjets EUP 572,220 sound waves. Sharp A sharp point is used SimpleDifficult to Tone-jet conductive to concentrate an constructionfabricate using point electrostatic field. standard VLSI processes for asurface ejecting ink- jet Only relevant for electrostatic ink jetsACTUATOR MOTION Volume The volume of the Simple High energy isHewlett-Packard expansion actuator changes, construction in thetypically required to Thermal Ink jet pushing the ink in all case ofthermal ink achieve volume Canon Bubblejet directions. jet expansion.This leads to thermal stress, cavitation, and kogation in thermal inkjet implementations Linear, The actuator moves in Efficient Highfabrication IJ01,IJ02,IJ04, normal to a direction normal to coupling toink complexity may be IJ07,IJ11,IJ14 chip surface the print headsurface. drops ejected required to achieve The nozzle is typicallynormal to the perpendicular in the line of surface motion movement.Parallel to The actuator moves Suitable for Fabrication IJ12,IJ13,IJ15,chip surface parallel to the print planar fabrication complexityIJ33,IJ34,IJ35, head surface. Drop Friction IJ36 ejection may still beStiction normal to the surface. Membrane An actuator with a Theeffective Fabrication 1982 Howkins push high force but small area of theactuator complexity U.S. Pat. No. 4,459,601 area is used to push abecomes the Actuator size stiff membrane that is membrane areaDifficulty of in contact with the ink. integration in a VLSI processRotary The actuator causes Rotary levers Device IJ05,IJ08,IJ13, therotation of some maybe used to complexity IJ28 element, such a grill orincrease travel May have impeller Small chip area friction at a pivotrequirements point Bend The actuator bends A very small Requires the1970 Kyser et al when energized. This change in actuator to be made U.S.Pat. No. 3,946,398 may be due to dimensions can he from at least two1973 Stemme differential thermal converted to a large distinct layers,or to U.S. Pat. No. 3,747,120 expansion, motion. have a thermalIJ03,IJ09,IJ10, piezoelectric difference across the IJ19,IJ23,IJ24,expansion, actuator IJ25,IJ29,IJ30, magnetostriction, or IJ31,IJ33,IJ34,other form of relative IJ35 dimensional change. Swivel The actuatorswivels Allows operation Inefficient IJ06 around a central pivot, wherethe net linear coupling to the ink This motion is suitable force on thepaddle motion where there are is zero opposite forces Small chip areaapplied to opposite requirements sides of the paddle, e.g. Lorenz force.Straighten The actuator is Can be used with Requires careful IJ26,IJ32normally bent, and shape memory balance of stresses straightens whenalloys where the to ensure that the energized. austenic phase isquiescent bend is planar accurate Double The actuator bends in Oneactuator can Difficult to make IJ36,IJ37,IJ38 bend one direction when beused to power the drops ejected by one element is two nozzles. both benddirections energized, and bends Reduced chip identical. the other waywhen size. A small another element is Not sensitive to efficiency lossenergized. ambient temperature compared to equivalent single bendactuators. Shear Energizing the Can increase the Not readily 1985Fishbeck actuator causes a shear effective travel of applicable to otherU.S. Pat. No. 4,584,590 motion in the actuator piezoelectric actuatormaterial, actuators mechanisms Radial con- The actuator squeezesRelatively easy High force 1970 Zoltan U.S. Pat No. striction an inkreservoir, to fabricate single required 3,683,212 forcing ink from anozzles from glass Inefficient constricted nozzle. tubing as Difficultto macroscopic integrate with VLSI structures processes Coil/uncoil Acoiled actuator Easy to fabricate Difficult to IJ17,IJ21,IJ34, uncoilsor coils more as a planar VLSI fabricate for non- IJ35 tightly. Themotion of process planar devices the free end of the Small area Poorout-of-plane actuator ejects the ink, required, therefore stiffness lowcost Bow The actuator bows (or Can increase the Maximum travelIJ16,IJ18,IJ27 buckles) in the middle speed of travel is constrainedwhen energized. Mechanically High force rigid required Push-Pull Twoactuators control The structure is Not readily IJ18 a shutter. Oneactuator pinned at both ends, suitable for ink jets pulls the shutter,and so has a high out-of- which directly push the other pushes it. planerigidity the ink Curl A set of actuators curl Good fluid flow DesignIJ20,IJ42 inwards inwards to reduce the to the region behind complexityvolume of ink that the actuator they enclose, increases efficiency CurlA set of actuators curl Relatively simple Relatively large IJ43 outwardsoutwards, pressurizing construction chip area ink in a chambersurrounding the actuators, and expelling ink from a nozzle in thechamber. Iris Multiple vanes enclose High efficiency High fabricationIJ22 a volume of ink. These Small chip area complexity simultaneouslyrotate, Not suitable for reducing the volume pigmented inks between thevanes. Acoustic The actuator vibrates The actuator can Large area 1993Hadimioglu vibration at a high frequency. be physically distant requiredfor et al, EUP 550,192 from the ink efficient operation 1993 Elrod etal, at useful frequencies EUP 572,220 Acoustic coupling and crosstalkComplex drive circuitry Poor control of drop volume and position None Invarious ink jet No moving parts Various other Silverbrook, EP designsthe actuator tradeoffs are 0771 658 A2 and does not move. required torelated patent eliminate moving applications parts Tone-jet NOZZLEREFILL METHOD Surface This is thenormal way Fabrication Low speedThermal ink jet tension that ink jets are simplicity Surface tensionPiezoelectric ink refilled. After the Operational force relatively jetactuator is energized, simplicity small compared to IJ01-IJ07,IJ10- ittypically returns actuator force IJ14,IJ16,IJ20, rapidly to its normalLong refill time IJ22-IJ45 position. This rapid usually dominates returnsucks in air the total repetition through the nozzle rate opening. Theink surface tension at the nozzle then exerts a small force restoringthe meniscus to a minimum area. This force refills the nozzle. ShutteredInk to the nozzle High speed Requires IJ08,IJ13,IJ15, oscillatingchamber is provided at Low actuator common ink IJ17,IJ18,IJ19, inkpressure a pressure that energy, as the pressure oscillator IJ21oscillates at twice the actuator need only May not be drop ejection openor close the suitable for frequency. When a shutter, instead ofpigmented inks drop is to be ejected, ejecting the ink drop the shutteris opened for 3 half cycles: drop ejection, actuator retum, and refill.The shutter is then closed to prevent the nozzle chamber emptying duringthe next negative pressure cycle. Refill After the main 4 High speed, asRequires two IJ09 actuator actuator has ejected a the nozzle isindependent drop a second (refill) actively refilled actuators pernozzle actuator is energized. The refill actuator pushes ink into thenozzle chamber. The refill actuator returns slowly, to prevent itsreturn from emptying the chamber again. Positive ink The ink is held aslight High refill rate, Surface spill Silverbrook, EP pressure positivepressure. therefore a high must be prevented 0771 658 A2 and After theink drop is drop repetition rate Highly related patent ejected, thenozzle is possible hydrophobic print applications chamber fills quicklyhead surfaces are Alternative for:, as surface tension and requiredIJ01-IJ07,IJ10-IJ14, ink pressure both IJ16,IJ20,IJ22-IJ45 operate torefill the nozzle. METHOD OF RESTRICTING BACK-FLOW THROUGH INLET Longinlet The ink inlet channel Design simplicity Restricts refill Thermalink jet channel to the nozzle chamber Operational rate Piezoelectric inkis made long and simplicity May result in a jet relatively narrow,Reduces relatively large chip IJ42,IJ43 relying on viscous crosstalkarea drag to reduce inlet Only partially back-flow. effective Positiveink The ink is under a Drop selection Requires a Silverbrook, EPpressure positive pressure, so and separation method (such as a 0771 658A2 and that in the quiescent forces can be nozzle rim or related patentstate some of the ink reduced effective applications drop alreadyprotrudes Fast refill time hydrophobizing, or Possible from the nozzle.both) to prevent operation of the This reduces the flooding of thefollowing: IJ01- pressure in the nozzle ejection surface ofIJ07,IJ09-IJ12, chamber which is the print head. IJ14,IJ16,IJ20,required to eject a IJ22,IJ23-IJ34, certain volume of ink.IJ36-IJ41,IJ44 The reduction in chamber pressure results in a reductionin ink pushed out through the inlet. Baffle One or more baffles Therefill rate is Design HP Thermal Ink are placed in the inlet not asrestricted as complexity Jet ink flow. When the the long inlet Mayincrease Tektronix actuator is energized, method. fabricationpiezoelectric ink jet the rapid ink Reduces complexity (e.g. movementcreates crosstalk Tektronix hot melt eddies which restrict Piezoelectricprint the flow through the heads). inlet. The slower refill process isunrestricted, and does not result in eddies. Flexible flap In thismethod recently Significantly Not applicable to Canon restrictsdisclosed by Canon, reduces back-flow most ink jet inlet the expandingactuator for edge-shooter configurations (bubble) pushes on a thermalink jet Increased flexible flap that devices fabrication restricts theinlet, complexity Inelastic deformation of polymer flap results in creepover extended use Inlet filter A filter is located Additional Restrictsrefill IJ04,IJ12,IJ24, between the ink inlet advantage of ink rateIJ27,IJ29,IJ30 and the nozzle filtration May result in chamber. Thefilter Ink filter may be complex has a multitude of fabricated with noconstruction small holes or slots, additional process restricting inkflow, steps The filter also removes particles which may block thenozzle. Small inlet The ink inlet channel Design simplicity Restrictsrefill IJ02,IJ37,IJ44 compared to the nozzle chamber rate to nozzle hasa substantially May result in a smaller cross section relatively largechip than that of the nozzle, area resulting in easier ink Onlypartially egress out of the effective nozzle than out of the inlet.Inlet shutter A secondary actuator Increases speed Requires separateIJ09 controls the position of of the ink-jet print refill actuator and ashutter, closing off head operation drive circuit the ink inlet when themain actuator is energized. The inlet is The method avoids the Back-flowRequires careful IJ01,IJ03,IJ05, located problem of inlet back- problemis design to minimize IJ06,IJ07,IJ10, behind the flow by arranging theeliminated the negative IJ11,IJ14,IJ16, ink-pushing ink-pushing surfaceof pressure behind the IJ22,IJ23,IJ25, surface the actuator betweenpaddle IJ28,IJ31,IJ32, the inlet and the IJ33,IJ34,IJ35, nozzle.IJ36,IJ39,IJ40, IJ41 Part of the The actuator and a Significant Smallincrease in IJ07,IJ20,IJ26, actuator wall of the ink reductions in back-fabrication IJ38 moves to chamber are arranged flow can be complexityshut off the so that the motion of achieved inlet the actuator closesoff Compact designs the inlet. possible Nozzle In some configurationsInk back-flow None related to Silverbrook, EP actuator of ink jet, thereis no problem is ink back-flow on 0771 658 A2 and does not expansion oreliminated actuation related patent result in ink movement of anapplications back-flow actuator which may Valve-jet cause ink back-flowTone-jet through the inlet. NOZZLE CLEARING METHOD Normal All of thenozzles are No added May not be Most ink jet nozzle firing firedperiodically, complexity on the sufficient to systems before the ink hasa print head displace dried ink IJ01,IJ02,IJ03, chance to dry. WhenIJ04,IJ05,IJ06, not in use the nozzles IJ07,IJ09,IJ10, are sealed(capped) IJ11,IJ12,IJ14, against air. IJ16,IJ20,IJ22, The nozzle firingis IJ23,IJ24,IJ25, usually performed IJ26,IJ27,IJ28, during a specialIJ29,IJ30,IJ31, clearing cycle, after IJ32,IJ33,IJ34, first moving theprint IJ36,IJ37,IJ38, head to a cleaning IJ39,IJ40,,IJ41, station.IJ42,IJ43,IJ44,, IJ45 Extra In systems which heat Can be highly Requireshigher Silverbrook, EP power to the ink, but do not boil effective ifthe drive voltage for 0771 658 A2 and ink heater it under normal heateris adjacent to clearing related patent situations, nozzle the nozzle Mayrequire applications clearing can be larger drive achieved by over-transistors powering the heater and boiling ink at the nozzle. Rapid Theactuator is fired in Does not require Effectiveness May be usedsuccess-ion rapid succession. In extra drive circuits depends with:IJ01,IJ02, of actuator some configurations, on the print headsubstantially upon IJ03,IJ04,IJ05, pulses this may cause heat Can bereadily the configuration of IJ06,IJ07,IJ09, build-up at the nozzlecontrolled and the ink jet nozzle IJ10,IJ11,IJ14, which boils the ink,initiated by digital IJ16,IJ20,IJ22, clearing the nozzle. In logicIJ23,IJ24,IJ25, other situations, it may IJ27,IJ28,IJ29, causesufficient IJ30,IJ31,IJ32, vibrations to dislodge IJ33,IJ34,IJ36,clogged nozzles. IJ37,IJ38,IJ39, IJ40,IJ41,IJ42, IJ43,IJ44,IJ45 ExtraWhere an actuator is A simple Not suitable May be used power to notnormally driven to solution where where there is a with: IJ03,IJ09, inkpushing the limit of its motion, applicable hard limit toIJ16,IJ20,IJ23, actuator nozzle clearing may be actuator movementIJ24,IJ25,IJ27, assisted by providing IJ29,IJ30,IJ31, an enhanced driveIJ32,IJ39,IJ40, signal to the actuator. IJ41,IJ42,IJ43, IJ44,IJ45Acoustic An ultrasonic wave is A high nozzle High IJ08,IJ13,IJ15,resonance applied to the ink clearing capability implementation costIJ17,IJ18,IJ19, chamber. This wave is can be achieved if system does notIJ21 of an appropriate May be already include an amplitude andimplemented at very acoustic actuator frequency to cause low cost insystems sufficient force at the which already nozzle to clear includeacoustic blockages. This is actuators easiest to achieve if theultrasonic wave is at a resonant frequency of the ink cavity. Nozzle Amicrofabricated Can clear Accurate Silverbrook, EP clearing plate ispushed against severely clogged mechanical 0771 658 A2 and plate thenozzles. The plate nozzles alignment is related patent has a post forevery required applications nozzle. A post moves Moving parts arethrough each nozzle, required displacing dried ink. There is risk ofdamage to the nozzles Accurate fabrication is required Ink The pressureof the ink May be effective Requires Maybe used pressure is temporarilywhere other pressure pump or with all IJ series ink pulse increased sothat ink methods cannot be other pressure jets streams from all of theused actuator nozzles. This may be Expensive used in conjunctionWasteful of ink with actuator energizing. Print head A flexible ‘blade’is Effective for Difficult to use if Many ink jet wiper wiped across theprint planar print head print head surface is systems head surface. Thesurfaces non-planar or very blade is usually Low cost fragile fabricatedfrom a Requires flexible polymer, e.g. mechanical parts rubber orsynthetic Blade can wear elastomer. out in high volume print systemsSeparate A separate heater is Can be effective Fabrication Can be usedwith ink boiling provided at the nozzle where other nozzle complexitymany IJ series ink heater although the normal clearing methods jets drope-ection cannot be used mechanism does not Can be require it. Theheaters implemented at no do not require additional cost in individualdrive some ink jet circuits, as many configurations nozzles can becleared simultaneously, and no imaging is required. NOZZLE PLATECONSTRUCTION Electro- A nozzle plate is Fabrication High Hewlett Packardformed separately fabricated simplicity temperatures and Thermal Ink jetnickel from electroformed pressures are nickel, and bonded to requiredto bond the print head chip. nozzle plate Minimum thickness constraintsDifferential thermal expansion Laser Individual nozzle No masks Eachhole must Canon Bubblejet ablated or holes are ablated by an required beindividually 1988 Sercel et drilled intense UV laser in a Can be quitefast formed al., SPIE, Vol. 998 polymer nozzle plate, which is Somecontrol Special Excimer Beam typically a polymer over nozzle profileequipment required Applications, pp. such as polyimide or is possibleSlow where there 76-83 polysulphone Equipment are many thousands 1993Watanabe required is relatively of nozzles per print et al., U.S. Pat.No. low cost head 5,208,604 May produce thin burrs at exit holes SiliconA separate nozzle High accuracy is Two part K. Bean, IEEE micro- plateis attainable construction Transactions on machined micromachined fromHigh cost Electron Devices, single crystal silicon, Requires Vol. ED-25,No. 10, and bonded to the precision aligmnent 1978, pp IJ85-IJ95 printhead wafer. Nozzles may be Xerox 1990 clogged by adhesive Hawkins etal., U.S. Pat. No. 4,899,181 Glass Fine glass capillaries No expensiveVery small 1970 Zoltan capillaries are drawn from glass equipmentrequired nozzle sizes are U.S. Pat. No. 3,683,212 tubing. This methodSimple to make difficult to form has been used for single nozzles Notsuited for making individual mass production nozzles, but is difficultto use for bulk manufacturing of print heads with thousands of nozzles.Monolithic, The nozzle plate is High accuracy Requires Silverbrook, EPsurface deposited as a layer (<1 μm) sacrificial layer 0771 658 A2 andmicro- using standard VLSI Monolithic under the nozzle related patentmachined deposition techniques. Low cost plate to form the applicationsusing VLSI Nozzles are etched in Existing nozzle chamber IJ01,IJ02,IJ04,litho- the nozzle plate using processes can be Surface may beIJ11,IJ12,IJ17, graphic VLSI lithography and used fragile to the touchIJ18,IJ20,IJ22, processes etching. IJ24,IJ27,IJ28, IJ29,IJ30,IJ31,IJ32,IJ33,IJ34, IJ36,IJ37,IJ38, IJ39,IJ40,IJ41, IJ42,IJ43,IJ44 NOZZLEPLATE CONSTRUCTION Monolithic, The nozzle plate is a High accuracyRequires long IJ03,IJ05,IJ06, etched buried etch stop in the (<1 μm)etch times IJ07,IJ08,IJ09, through wafer. Nozzle Monolithic Requires aIJ10,IJ13,IJ14, substrate chambers are etched in Low cost support waferIJ15,IJ16,IJ19, the front of the wafer, No differential IJ21,IJ23,IJ25,and the wafer is expansion IJ26 thinned from the back side. Nozzles arethen etched in the etch stop layer. No nozzle Various methods have Nonozzles to Difficult to Ricoh 1995 plate been tried to eliminate becomeclogged control drop Sekiya et al the nozzles entirely, to positionaccurately U.S. Pat. No. 5,412,413 prevent nozzle Crosstalk 1993Hadimioglu clogging. These problems et al EUP 550,192 include thermalbubble 1993 Elrod et al mechanisms and EUP 572,220 acoustic lensmechanisms Trough Each drop ejector has Reduced Drop firing IJ35 atrough through manufacturing direction is sensitive which a paddlemoves, complexity to wicking. There is no nozzle Monolithic plate.Nozzle slit The elimination of No nozzles to Difficult to 1989 Saito etal instead of nozzle holes and become clogged control drop U.S. Pat. No.4,799,068 individual replacement by a slit position accurately nozzlesencompassing many Crosstalk actuator positions problems reduces nozzleclogging, but increases crosstalk due to ink surface waves DROP EJECTIONDIRECTION Edge Ink flow is along the Simple Nozzles limited CanonBubblejet (‘edge surface of the chip, construction to edge 1979 Endo etal GB shooter’) and ink drops are No silicon High resolution patent2,007,162 ejected from the chip etching required is difficult Xeroxheater-in- edge. Good heat Fast color pit 1990 Hawkins et sinking viasubstrate printing requires al U.S. Pat. No. 4,899,181 Mechanically oneprint head per Tone-jet strong color Ease of chip handing Surface Inkflow is along the No bulk silicon Maximum ink Hewlett-Packard (‘roofsurface of the chip, etching required flow is severely TIJ 1982 VaughtCt shooter’) and ink drops are Silicon can make restricted al U.S. Pat.No. 4,490,728 ejected from the chip an effective heat IJ02,IJ11,IJ12,surface, normal to the sink IJ20,IJ22 plane of the chip. Mechanicalstrength Through Ink flow is through the High ink flow Requires bulkSilverbrook, EP chip, chip, and ink drops are Suitable for siliconetching 0771 658 A2 and forward ejected from the front pagewidth printrelated patent (‘up surface of the chip. heads applications shooter’)High nozzle IJ04,IJ17,IJ18, packing density IJ24,IJ27-IJ45 therefore lowmanufacturing cost Through Ink flow is through the High ink flowRequires wafer IJ01,IJ03,IJ05, chip, chip, and ink drops are Suitablefor thinning IJ06,IJ07,IJ08, reverse ejected from the rear pagewidthprint Requires special IJ09,IJ10,IJ13, (‘down surface of the chip. headshandling during IJ14,IJ15,IJ16, shooter') High nozzle manufactureIJ19,IJ21,IJ23, packing density IJ25,IJ26 therefore low manufacturingcost Through Ink flow is through the Suitable for Pagewidth print EpsonStylus actuator actuator, which is not piezoelectric print heads requireTektronix hot fabricated as part of heads several thousand meltpiezoelectric the same substrate as connections to drive ink jets thedrive transistors. circuits Cannot be manufactured in standard CMOS fabsComplex assembly required INK TYPE Aqueous, Water based ink whichEnvironmentally Slow drying Most existing ink dye typically contains:friendly Corrosive jets water, dye, surfactant, No odor Bleeds on paperAll IJ series ink humectant, and May jets biocide. strikethroughSilverbrook, EP Modem ink dyes have Cockles paper 0771 658 A2 and highwater-fastness, related patent light fastness applications Aqueous,Water based ink which Environmentally Slow drying IJ02,IJ04,IJ21,pigment typically contains: friendly Corrosive IJ26,IJ27,IJ30 water,pigment, No odor Pigment may Silverbrook, EP surfactant, humectant,Reduced bleed clog nozzles 0771 658 A2 and and biocide. Reduced wickingPigment may related patent Pigments have an Reduced clog actuatorapplications advantage in reduced strikethrough mechanisms Piezoelectricink- bleed, wicking and Cockles paper jets strikethrough. Thermal inkjets (with significant restrictions) Methyl MEK is a highly Very fastdrying Odorous All IJ series ink Ethyl volatile solvent used Prints onvarious Flammable jets Ketone for industrial printing substrates such as(MEK) on difficult surfaces metals and plastics such as aluminum cans.Alcohol Alcohol based inks Fast drying Slight odor All IJ series ink(ethanol, 2- can be used where the Operates at sub- Flammable jetsbutanol, printer must operate at freezing and others) temperatures belowtemperatures the freezing point of Reduced paper water. An example ofcockle this is in-camera Low cost consumer photographic printing. PhaseThe ink is solid at No drying time- High viscosity Tektronix hot changeroom temperature, and ink instantly freezes Printed ink meltpiezoelectric (hot melt) is melted in the print on the print mediumtypically has a ink jets head before jetting. Almost any print ‘waxy’feel 1989 Nowak Hot melt inks are medium can be used Printed pages U.S.Pat. No. 4,820,346 usually wax based, No paper cockle may ‘block’ All IJseries ink with a melting point occurs Ink temperature jets around 80°C. After No wicking may be above the jetting the ink freezes occurscurie point of almost instantly upon No bleed occurs permanent magnetscontacting the print No strikethrough Ink heaters medium or a transferoccurs consume power roller. Long warm-up time Oil Oil based inks areHigh solubility High viscosity: All IJ series ink extensively used inmedium for some this is a significant jets offset printing. They dyeslimitation for use in have advantages in Does not cockle ink jets, whichimproved paper usually require a characteristics on Does not wick lowviscosity. Some paper (especially no through paper short chain andwicking or cockle). multi-branched oils Oil soluble dies and have asufficiently pigments are required. low viscosity. Slow drying Micro- Amicroemulsion is a Stops ink bleed Viscosity higher All IJ series inkemulsion stable, self forming High dye than water jets emulsion of oil,water, solubility Cost is slightly and surfactant. The Water, oil, andhigher than water characteristic drop size amphiphilic soluble based inkis less than 100 nm, dies can be used High surfactant and is determinedby Can stabilize concentration the preferred curvature pigment required(around of the surfactant. suspensions 5%)

I claim:
 1. A method of operating an ink jet nozzle arrangement, themethod comprising the steps of: maintaining an ink ejection port of anozzle chamber normally closed; subjecting ink in an ink reservoir to anoscillating pressure, the reservoir being in communication with thenozzle chamber; and when it is desired to eject ink from the inkejection port, opening the ink ejection port so that ink is ejectedunder the effect of the oscillating pressure.
 2. The method of claim 1which includes ejecting the ink on a first cycle of positive pressureapplied to the ink, ink drop break-off occurring on a first cycle ofnegative pressure applied to the ink.
 3. The method of claim 2 whichincludes maintaining the ink ejection port open during a second cycle ofpositive pressure to facilitate refilling of the nozzle chamber from theink reservoir.
 4. The method of claim 3 which includes closing the inkejection port before a second cycle of negative pressure for inhibitingwithdrawal of ink from the nozzle chamber.
 5. The method of claim 1 inwhich said ink jet nozzle arrangement forms part of an array of ink jetnozzle arrangements which includes varying the amplitude of the pressurein the ink reservoir in response to viscosity of the ink and the numberof drops to be ejected from the array.
 6. An ink jet nozzle arrangementwhich comprises: a nozzle chamber defining means which defines a nozzlechamber and which includes a wall having an ink ejection port definedtherein; an ink reservoir, the ink reservoir being in communication withthe nozzle chamber; a pressure generating means associated with thereservoir for imparting an oscillating pressure to ink in the reservoir;and a shutter associated with the ink ejection port for opening andclosing the ink ejection port, the port being opened on demand so thatvariations in pressure in the reservoir cause ink ejection through saidport.
 7. The arrangement of claim 6 in which the pressure generatingmeans is arranged in the reservoir.
 8. The arrangement of claim 6 inwhich the pressure generating means is a transducer.
 9. The arrangementof claim 8 in which the transducer is an ultrasonic transducer.
 10. Thearrangement of claim 6 in which the shutter is mounted on an actuator,activation of the actuator on demand causing the shutter to move out ofalignment with the ink ejection port to open the ink ejection port. 11.The arrangement of claim 10 in which the actuator is an electro-thermalbend actuator.